Trump's former White House national security advisor made veiled threats against a NATO ally, taking the Greenland issue in a bizarre direction.

Former national security adviser Robert O’Brien said in a Sunday interview that Denmark should let the U.S. “buy” Greenland if it cannot defend the self-governing country, noting the territory

Corey Lewandowski, a senior adviser to Donald Trump, defended the president-elect's desire to take over Greenland by arguing his boss was a "real estate master." During a Monday interview on Newsmax,

President-elect Donald Trump shared his renewed interest Sunday in the U.S. controlling the autonomous territory of Greenland, which is owned by Denmark.

Denmark needs to do more than add dog sleds to defend Greenland, given its icy territory has it “on the front lines of the war against Russia and China,” ex-National Security Adviser Robert O’Brien said Sunday.